There have been substantial advances in molecular and cellular biology that have provided new insight into the biochemical and genetic basis of lymphocyte recognition, activation and expression of distinct functional phenotypes. It has now become evident that for both T and B cells, stimuli delivered through their receptors can result in either clonal expansion or apoptosis. In the case of T cells, clonal expansion of helper cells is accompanied by differentiation into two major functional subsets that regulate the immune response. The pathways and the molecular components between the membrane and the nucleus are an area of very active investigation. This meeting will draw together scientists working on diverse aspects of this problem, including receptor ligand interactions, intracellular pathways that transmit receptor mediated signals and the effect of such signal transduction pathways on gene regulation. The aim of this meeting is to integrate the information from these various experimental approaches into a new synthesis and molecular explanation of T cell activation, differentiation and death. The small meetings (Gordon, FASEB Summer Conference) are excellent meetings that typically do not have a unified theme but touch on the latest highlights in all of immunology. Further, they are accessible to a very limited number of scientists (approximately 100) with representation of senior scientists and very little space for junior faculty members, post-doctoral fellows and graduate students. Large meetings such as FASEB (AAI) do allow the attendance of the latter individuals but are not subsumed under a single theme either. The Keystone Symposia has the advantage of allowing a large number of junior scientists and scientists in training to attend a meeting focused under a single theme, in this case T-lymphocyte activation, signaling and death.